The use of acrylic or methacrylic acid esters for dental, medical, and technical purposes, especially for the manufacture of plastic dental prostheses or their linings, when the prosthesis fit has changed in the course of time, as well as their use for taking jaw impressions, etc. is known. It is also known to add additives, such as plastics of other types, cellulose derivatives, natural resins (such as Kopal, Sandarac), paraffin, wax, oil, dye and fillers, to the acrylic or methacrylic acid esters for this purpose. Acrylic or methacrylic acid esters are generally used in the form of a powder, bead, or chip granulate of the polymer or mixed polymers of these compounds dissolved in a liquid monomer, usually methacrylic acid methyl ester, and this solution is caused to harden, possibly with the addition of promoters. This process suffers from several disadvantages.
Dissolving the powder in the liquid is relatively time-consuming. In cold polymerization in a powder-liquid system, it is known that parts of the polymer are easily left undissolved, resulting in a loss of stability and homogeneity of the resultant product. Cold polymers based upon monomeric methyl methacrylate are also harmful to mucous membranes. Moreover, burns can result from processing these cold polymers in the mouth, for example when polymerization is allowed to proceed rapidly. In the manufacture of linings from such monomeric methyl methacrylate solutions, the resultant products do not always have perfectly smooth surfaces and are therefore more likely to be attacked by the microflora in the mouth because they partially adsorb saliva. In addition, such products also suffer from undesirable "shrinkage."